Abstract (30 lines) A promising, new quantitative cardiac risk-calculator, the HEART score (History, Electrocardiogram findings, Age, Risk factors, and Troponin value), has recently been proposed as a useful aid for guiding disposition de- cisions for patients with potential cardiac chest pain (CP) after inconclusive Emergency Department (ED) eval- uation. Derived and validated on Dutch ED patients and externally validated in an Asian-Pacific cohort, this simple outcome predictor has been shown to accurately quantify the likelihood of a major adverse cardiac event (MACE) within 30 days of an index visit, and has outperformed other decision aids as well as clinical ge- stalt in rigorously controlled clinical trials. What we don't know is the performance characteristics of the HEART score when applied in the context of the U.S. healthcare system, the feasibility and practicality of studying it in the setting of a busy U.S. ED., and what its relative ease of use is compared with other options. The objective of this pilot study is to determine the feasibility and practicality of conducting a large R01-funded clinical trial to determine the value of the HEART score in discriminating low- from moderate-risk CP among ED patients in the U.S. The rationale for this pilot study is that an instrument that will guide clinical practice and impact dispo- sition decisions must be tested for accuracy and convenience in order to be effectively used in a busy ED prac- tice. Our central hypothesis is that the HEART score will be feasible to test, will have acceptable reliability, and superior ease of use, making it suitable as a decision aid to safely reduce unnecessary admissions and pro- mote provider disposition consistency. Our aims are to 1) test the feasibility of conducting a study evaluating the HEART score in real-time within the practice setting of a busy U.S. ED, using enrollment and completion of follow-up as endpoints, 2) to generate preliminary data for the HEART score's ability to discriminate between low- and moderate-risk cardiac ED patients in a prospective observational study, and 3) measure and compare providers' self-reported ease of use for the HEART score. When we accomplish our aims, we will 1) provide the foundation for our planned R01 proposal by generating preliminary data for the HEART score's ability to discriminate between low- and moderate-risk CP among patients in the U.S. and 2) verify the HEART score's ease of use. What we propose is innovative in that this approach to studying the HEART score decision aid within the ED practice setting has never before been done. This work is significant because it constitutes the first step in defining the HEART score's performance characteristics in a U.S. ED setting, outside of a con- trolled clinical trial before it can be safely incorporated into clinical pathways. Further, this issue is ubiquitous in emergency medicine ? inconsistent disposition decisions for this chief complaint are the leading cause of prac- tice variability in this country, potentially affecting hundreds of thousands of Americans annually. This line of investigation will decrease CP admission disparities and optimize resource utilization, which will improve the quality, safety, efficiency, and effectiveness of health care.